1. Field of the Invention
The present invention relates to a base material of a frame for a Braun tube and a method for manufacturing the frame, and more particularly, the present invention relates to an improvement in a method for manufacturing a frame which supports a shadow mask used in a Braun tube or a picture tube such as a color Braun tube (CRT), a color tube (CPT), a color display tube (CDT) or the like.
2. Description of the Related Art
As shown in FIG. 7, in a color Braun tube, etc., a frame F is used for supporting a shadow mask which is a plate having a screen-shaped configuration and is extremely thin, such that it is intervened as a connecting holder plate between a panel P and a funnel F.
A plate having a rectangular configuration is used as a base material suitable for manufacturing a frame for a Braun tube. Generally, a frame for a Braun tube is manufactured by pressing the base material having a predetermined thickness through a series of machining processes including blanking, drawing and piercing, to a thin metal plate.
A window is defined in a center portion of the frame to be used as an opening through which beams injected from an electron gun can be passed. The window is defined by piercing the center portion of the frame to form the opening, and a segment cut out from the frame by the piercing process is discarded. Accordingly, due to the fact that the segment is discarded as scrap, material is wasted. Further, a base material to be formed as a frame must have a dimension which is larger than a predetermined one. This is because there exists a limit in a drawing rate when a solid plate material is subjected to a drawing process.
Hence, the frame manufactured according to the related art suffers from defects in that since a base material must have a dimension greater than a predetermined one and a segment cut out from a center portion thereof is discarded, material is wasted, and since remarkable power loss is caused in a press machine, manufacturing cost is increased.
In other words, referring to FIGS. 1 through 3, there are shown perspective views which illustrate a base material of a frame for a Braun tube and explain machining processes adopted for manufacturing the frame.
As shown in FIG. 1, a base material 1 used in manufacturing a frame for a Braun tube according to the related art has substantially a rounded rectangular configuration. In case of a 14 inch Braun tube, the base material has a dimension including a width of 276 mm, a height of 326 mm, a thickness of 1.2 mm and a weight of 0.85 kg.
The base material 1 is drawn to obtain a basic frame-shaped workpiece 2 as shown in FIG. 2, and a segment 4 is cut out from a center portion of the base material 1 by a piercing process to define a central window 3 as shown in FIG. 3. At this time, the segment 4 cut out from the base material 1 is discarded as scrap.
However, in the manufacturing method of the related art, since the base material 1 is a solid plate material, a minimum dimension thereof for enabling a drawing process to be implemented must not be decreased from that described above. Accordingly, it is considered to be difficult to save material without a change in mechanical property which requires a great deal of research and investment.